Steel sucker rod and the like and its production



w. J. CROOK 1,764,068

STEEL SUCKER ROD AND THE LIKE AND ITS PRODUCTION June 17, 1930.

Filed Jan. 8, 1927 Patented June 17, 1930 UNITED STATES PATENT OFFICE WELTON J'. CROOK, OF STANFORD UNIVERSITY, CALIFORNIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO EMSCO DERRICK & EQUIPMENT COMPANY, OF CALIFORNIA, A CORPORATION OF CALIFORNIA LOS ANGELES,

STEEL SUCKER ROD AND THE LIKE AND ITS PRODUCTION Application filed January 8, 1927. Serial No. 159,808.

This invention has to dowith the production of steel sucker rods and other steel products called upon to resist stresses and strains similar to those to which such rods areexposed. It is also concerned with the rods or like products produced by the method herein set forth.

The invention is peculiarly applicable to sucker rods and was evolved to meet a serious, universally acknowledged situation which has arisen in the oil pumping art. Therefore, I will hereinafter describe the invention as applied only to sucker rods, but this description of a single particular prod:

not and its production will serve to advise those skilled in the art how the invention may be appliedwith advantage to other products and their production and is in no way to be considered as limitative on the invention, considered in its broader aspects. Sucker rods are made up from round stock in lengths of about twenty-five feet. They are swedged or upset to provideso-called pins which include enlarged wrench-taking portions of polygonal cross-section near the rod ends, there being annular flanges forged at opposite ends of each portion. The outermost flanges present shoulders at the base of cylindrical studs formed at the extreme ends of the rods. These studs are later threaded to take collars whereby the individual rods are coupled to one another to form a string of sucker rods adapted to extend from reciprocating mechanism at the top of a well to a pump plunger at the well bottom.

The total load on the rods is of very considerable magnitude, the rods, especially at the junction point of the threaded and wrench-taking portions, being subjected to very heavy stresses and strains, and most particularly to fatigue stresses. The depths of wells have'been increasing steadily, and in order to withstand the consequent increase of rod loads and stresses, the carbon content of the rods has been raised correspondingly. This naturally has been accompanied by a coincident tendency to increase the brittleness of the rods until it has finally reached 59 the point where rod failures (1116 to overbrittleness have become frequent occurrences. The serious aspect of this condition is of common knowledge to those skilled in the art. Therefore, it is the principal object of my lnvention to produce rods having the requisite high degrees of tensile strength and resistance to fatigue and yet having proper ductility, to the end that the rods may be well suited to withstand the most severe service conditions to which they are exposed.

It has been observed that by far the greater proportion of rod and pin failures is due to fatigueand that fatigue failure is most liable to occur in the ferrite areas of slowly cooled steel containing less than 0.9% carbon.

I have discovered that if, instead of raising the carbon content of the steel to resist failure under heavy load, a steel of comparatively low carbon content and containing a proper proportion of manganese is chosen and if after the pins have been formed'on the rod ends by proper forging and machin-' ing operations, the steel is suitably heat treated, there is obtained a rod and pin superior to those previously produced.

Generally stated, mymethod includes the forging of pins, in any suitable manner, on the end of normal steel rods containing from 0.26% to not more than 0.50% carbon and between 0.40% and 1% manganese. After the forging step, the pins are machined (usually including a threading operation) in cold state. The rods with their forged and machined pins, or the pin-portions of the rods. alone. are then heated to a temperature above the transformation point or critical range and comparatively rapidly quenched in oil or other suitable quenching medium.

In practicing this process I have made numerous tests both in the laboratory and in Percent Carbon 0.30 Manganese 0.60 Phosphorus 0.008

Before being subjected to the heat treatment, the pins were tested andv showed an ultimate strength of 7 9,360 pounds per square inch and pounds per square inch, an elastic limit of 80,000 pounds per square inch and an elon-.

gation of 27% in two inches, as against the properties shown above in the untreated sucker rod. The ductility of the treated steel was such that it could be bent flat in the cold state without fracture or crack.

Another test'made on standard test bars machined from forged and heat treated rod pins gave an ultimate stren h of 99,200 pounds per square inch, an e astic limit. of 67,600 pounds per square inch with an e1on-' ggtion of 20% in 2" and,a reduction of area 0 54%.

The following is a table setting forth the 7 details of the tests above mentioned:

tion but merely as illustrative of what appeared to give the best results for the par ticular purpose at hand. Therefore, in prac ticing my process, it will be borne in mind that some temperature above the critical range may beselectedfor the heating. In the class of steel with which this invention is concerned, the critical ranges will occur between 1300 and 17 00 Fahrenheit. Also, the time of heating will determine to some extent the exact temperature, since when the time of the heating is increased a lower temperature will in the art, andthe various times and temper- All this is well understood by those skilled atures will be modified. according to the exforged, cooled, then heated for 30 minutes at.

1600 Fahrenheit and quenched in oil; and

Treatment of bars er rod.

Bar No 1 a a 4 a 0 Temperature of quench 1600 1600 1600 1600 i 1550 1500 Time at quench temperature 30 min. 30 min. 30 min. 30 min. 30 min. 30 min,

Condition of bar Plain. Plain. I Plain. Threaded. Threaded. Threaded- Designation 0! steel used 01d stock. New stock. New stock. New stock. New stock. New stock;

Bar N v 1 s 9 I 10 Temperature of quench 1600 1000 Not quenched. Not quenched.

Time atguench temperature i 30 min. Condition of bar Machined pin. Machined pin. As tolled. As ro'lled.

Designation of steel used .4..- 01d stock. 01d stock. 01d stock. 01d stock.

Results of physical tests Bar N o.-. 1 2 3 4 6 Ultustrength pounds per sq. inch 95,755 100,001 100, 302 135,000 135,000 Elast. limit pounds per sq. inch. 0a, 205 70, 058 L81, 040 104, 700 104, 200 Elongation in 2' 28 per cent. 10 per cent. 10 per cent. 9 per cent.

Reduction ar Bar N e 7 s 0 i0 Ult. strength pounds per sq. inch 138,000 00, 201 00, 240 v 00,170 70,300 Elast. 1mm pounds per sq. inch 101, 000 68, 921 66,416 42, 352 40, 400

Elongation in 2" 9 per cent. 20 per cent. 20 per cent. 42 per cent. Lost.

' Reduction area i 54 per cent. 54 per cent.

The temperatures and times mentioned Fig. 3 is a fragmentary elevation of a suck- The sucker rod shown fragmentarily in Fig. 3 is made up from a round bar 10, the end thereof being upset or forged, when hot, to provide a wrench-taking portion 11 between annular collars 12 and 13. The stud end 14 is subsequently machined and threaded while the bar is in cold state.

The entire bar or, if desired, only the pin 15 which may be considered as including only stud 14 or both the stud and portion 11, is then heated to a temperature above the transformation point or of from 1300- to 1700 Fahrenheit. This temperature is held for a period of from ten minutes to an hour or crystallized out owing to the relatively slow rate of cooling in oil as compared with that which would result from water quenching.

It is considered that heating to 1600 Fahrenheit for thirty minutes has converted the iron from the alpha to the gamma state and enabled the cementite of the original pearlite to break down and form a solid solution of carbon in gamma iron, this being known as austenite. In order that a homogeneous austenite may form, the carbon from the pearlite must have time to migrate or diffuse at least across the distance equal to one half the aver age diameter of one ferrite grain as measured in the original steel.

The austenite formed when the quench temperature has been sufiiciently high and has been maintained sufliciently long, e. g 160 0 Fahrenheit for thirty minutes so that the carbon is completely diffused, cannot be preserved as such in steel of 0.30% to 0.50% carbon unless the cooling is very rapid-and 1n the present process the austenite during quenching transforms into martensite. Also when an oil quench is used, as in the present process, some small amount of free ferrite will come out of solution again.

This martensitic structure as produced in sucker rods has very different physical properties from that found in untreated rods made from the same. grade and quality of steel. The ultimate strength, upon which fatigue limit has been found to depend, was found to be over 100,000 pounds per square inch but at the same time the treated rod was -It should be borne in mind that the present invention has to do, not with an alloy steel, but with sucker rods made from plain carbon steel. I am well aware that alloy steels and plain carbon steels have been heat treated for the purpose of altering their physical properties. However, so far as I am aware, there have not previously been produced plain carbon steel sucker rods, of (the composition previously stated, which showed in well tests the physical properties or the resistance to fatigue failure that have been found in sucker rods produced by this process.

By subjecting sucker rods of the proper composition to the present process, the strength of the rods may be increased to a point equalling that of high carbon steels but at the same time the rods retain the ductility of low carbon steels with a greatly added resistance to'fatigue breakage.

Actual well tests of a million feet of these rods have resulted in no pin breakage in a period of over fourteen weeks whereas in two of the test wells, at least, no other rods have withstood over two weeks operation without pin breakage. The importance of these results in oil well operation is obvious I claim:

1. A method of producing plain carbon steel sucker rods and the like of high tensile strength and sufiicient ductility for oil well pumping and similar purposes, having a high fatigue resistance as herein mentioned, which includes heating, after forging and machining, sucker rods containing between 0.26% and 0.50% carbon and between 0.5% and 1% manganese to a temperature above the transformation point, and quenching rapidly as a final step in the process.

2. A method of producing plain carbon steel sucker rods of high tensile strength and suflicient ductility for oil well pumping and similar purposes, having a high fatigue resistance as herein mentioned, which includes heating, after forging and machining, sucker rods containing between 0.26% and 0.50% carbon and between 0.5% and 1% manganese, to a temperature of from 1300 to 17 00 Fahrenheit, holding this temperature for a period of at least ten minutes, and quenching rapidly in a suitable medium as a final step in the process.

3. The method of increasing the ultimate strength and resistance to fatigue and et retaining the ductility of carbon steel suc er rods, the ends of which have been forged and machined to form pins by subjecting said rods, containing between 0.26% and 0.50% carbon and between 0.5% and 1% manganese, to heat at a temperature above the transformation point and for a sulficient period of time to brlng about complete migration of carbon across the'ferrite ains and then quenching the steel rapi y in suitable medium as a final step in the process.

4. 'A method of producing plain carbon steel. suckerro'ds ofhigh tensile strength and sufiicient ductility for oil well pumping and similar purposes, having a high fatigue-'re-i :sistance as herein mentioned, which includes heating, after for ing and machining, sucker rods containing etween 0.26% and 5.50%

- carbon and between-0.5% and -1\%manganose, to a temperature of from 1300 to 17009.1.

Fahrenheit, holding this temperature forflf a period ofat least ten minutes, and quenching rapldlyin an'oil bath asadinal step in the process. o a i 5TA method of producinglain carbon steel suckgl rods and the like-o high tensile strength d sufiicient ductilit for oil well umping and similar purposes, aving {thigh atigue resistance as herein -meutionemwv hich I includes heating, after forging and'machining, sucker rods containing 'between0.26%

and 0.50% carbon-andbetween 0.5% and 1% manganeseto a tem erature above the transformation point, an quenching rapidly in an 'oil' bath as a final step in the process. 6. The method of increasing the ultimate -strength and resistance to fatigue and yet retaining the ductility ofcarbon steel sucker rods, the ends of which have been forged and machined to form pins, by subjecting said 3 rods, containing between 0.26% and 0.50%

' carbon and between 0.5% and 1% manganese,

to heating at 'a" temperature above the transformation point and for a sufiicient period of time to bring about complete migration of as carbon across the ferrite grains and'f'then 'Peten t No. l,764, f

quenchinft he steel rapidly in oil as a final step in- "e process.

a witness-thatlclaim the foregoin Iha'v ehereunto subscribed my name this 1 th day f1; -'W'ELTON J. CROOK.

egimricam on cokimcrioii.

WELTON J. ckoox.

Graiited June 1'1, 1m,,a-- I it. is hereby certified that error :appeafrs in the. print ed specification oi the a Qabove'numhered patent requiring correction as follows: i Page 4, line 7, claim I 4, for "5.50%" rea'd; "0.50%"; and that the said Letters Patentshouldbe read with this correction jtherein that the maitconform to the re cor'd'ofthe case iii the Patent Office.

si ne and mud this zine-(n3 ouui fA. 01-1930- I WmJALKionam' (Seal) i Acting Comissioner ofPatentu 

